In general, a silicon wafer is formed by a single crystal growing process for manufacturing a single crystal ingot, a slicing process for obtaining a thin disk-shaped wafer by slicing the single crystal ingot, a grinding process for machining an outer peripheral portion of a wafer to prevent cracking and distortion of the wafer obtained by the slicing process, a lapping process for removing damages due to mechanical processing remaining on the wafer, a polishing process for polishing the wafer, and a cleaning process for removing an abrasive or an foreign substance adhering to the wafer while polishing the polished wafer.
For a single crystal growth, a floating zone (FZ) method or a Czochralski (CZ) method (hereinafter referred to as CZ method) has been widely used. The CZ method is the most common method among these methods.
In the CZ method, a polycrystalline silicon is charged in a quartz crucible and heated and melted by a graphite heating element, and then a single crystal silicon ingot is grown by pulling up a seed crystal while rotating the seed crystal when the seed crystal is immersed in silicon melt formed as a result of melting and crystallization occurs at an interface.
In particular, oxygen is included in a silicon single crystal as crystal defects due to growth history and undesired impurities in a growing process of the silicon single crystal, and thus intruded oxygen in this manner is grown into oxygen precipitate due to heat applied during a manufacturing process of a semiconductor device. Although the oxygen precipitate shows beneficial characteristics such as reinforcing the strength of the silicon wafer and capturing metal pollution elements and serving as an internal gettering site, a leakage current and a fail of the semiconductor device are caused.
Accordingly, oxygen concentration of a wafer manufactured from the silicon single crystal ingot needs to be uniform in longitudinal and radial directions, and the oxygen concentration may be controlled through a seed rotating speed, a crucible rotating speed, a melt gap, which is the distance between a melt surface and a heat shield, a pull speed of the ingot, a design change of hot zone, a third element doping such as nitrogen or carbon, which are process variables when growing a silicon single crystal ingot.
However, in the case of a wafer obtained from a silicon single crystal ingot currently manufactured, in particular, a region where the oxygen concentration is non-uniform in a ring shape is found at an edge, which may be caused by non-uniformity of the internal gettering property described above.